Ultra‐Sharp Circular Dichroism Induced by Twisted Layered C4 Oligomers

Abstract

Chiral metamaterials consisting of sub‐wavelength asymmetric unit cells exhibit different optical responses on circularly polarized states of incident light. Chiral metamaterials with strong chiroptical activities provide sensitive sensors, finer spectrometers, and high‐performance encryption techniques. With these advantages, many types of chiral metamaterials have been researched; twisted layered metamaterials and oligomers that consist of nanoparticles have been reported for engineered chiral properties. C4 chiral metamaterials minimize conversion of polarized states and oligomers support exotic resonant modes to enable chiral encoding. Twisted‐layered chiral metamaterials to connect optical properties between C4‐chirality and oligomers are described. These twisted‐layered chiral metamaterials have both properties of non‐conversion efficiencies from C4‐chirality and encodable circular dichroism spectra that are caused by relative positions of oligomers. They exhibit ultra‐sharp circular dichroism in the near‐infrared region. The sharp circular dichroism is induced by interactions among layers in the metamaterials. Characteristics of the interactions are analyzed by considering electric field distribution profiles. These chiroptical properties of the twisted layered chiral metamaterials may have wide applications, including spectroscopy, thermal detector, and biochemical distributors.

Tunable metasurfaces towards versatile metalenses and metaholograms: a review

“…Propagation phase has been investigated by exploiting an effective refractive index to manipulate the retardation phase by changing the volume ratio, aspect ratio, and height of meta-atoms. 10,11 Resonant effects such as plasmonic resonance, [12][13][14][15] Mie resonance, 16,17 and Fabry-Pérot resonance 18,19 have also been exploited. By exploiting these resources, optical elements can be highly miniaturized and various optical applications have been implemented, such as beam splitters, [20][21][22] absorbers, [23][24][25][26][27][28][29] metalenses, 30,31 metaholograms, [32][33][34][35][36][37][38][39][40] selective thermal emitters, [41][42][43] detecting devices, [44][45][46] and structural color.…”

Planar Achiral Metasurfaces-Induced Anomalous Chiroptical Effect of Optical Spin Isolation

“…Furthermore, such a chiroptical effect of metasurfaces can be exploited for pragmatic photonic device applications such as chirality-induced color filters, cryptographic nanoprints, and anticounterfeiting holograms, , and the proposed design methodology will provide an insight into chirality and asymmetric transmission manipulation within near-/far-field light–matter interactions. ,− Moreover, such optical isolation metasurfaces can be developed further to increase the encrypted information density in a single device using a new concept like helical dichroism using the orbital angular momentum of light, which may enable holographic video displays. − …”

Ultrathin Suspended Chiral Metasurfaces for Enantiodiscrimination

“…[39][40][41] Electron beam lithography (EBL) and focused ion beam (FIB) have also been widely used to fabricate chiral metamaterials at the nanoscale. For example, a few kinds of chiral metamaterials made by EBL or FIB, such as multilayer nanoarrays, [42][43][44][45] kirigami structures, [46] and chiral nanoholes arrays, [29,47] have demonstrated intriguing chiroptical features of giant CD, [48][49][50] excellent rotation of linearly polarized lights, [51] and helical dichroism. [52] Nevertheless, the processing of fabrication for multilayer chiral metamaterials is sophisticated and requires multiple steps of precise alignment in EBL.…”